Dorothy Bruns, 44, was found dead inside her home on Tuesday. Authorities say pills and a note were found near her body.
Bruns faced up to 15 years in prison after being charged with manslaughter, criminally negligent homicide, reckless endangerment and assault following the accident in March.
Authorities say Bruns suffered a seizure before the incident. Her car drove forward, killing Ruthie Ann Blumenstein's 4-year-old daughter and the 1-year-old son of another parent. Blumenstein later lost her unborn child.
Prosecutors say doctors had told Bruns not to drive after she had a previous medical episode.